The truncation that underpaid interest for eleven years
I have been asked a few times on here what the worst bug of my career was. It was not mine, but I was the one who found where it lived, so I will tell it. In 2009 a retired schoolteacher walked into one of our branches with a passbook and a pocket calculator. She had been computing her own savings interest every month since 1998, out of habit, and for eleven years our figure had been a few cents lower than hers.…